Fluid dispensers have been used to mix a liquid chemical into the flow of water from a hose. The chemical, which might be a fertilizer or an insecticide, can then be sprayed on lawns, plants, and bushes.
Some fluid dispensers are mounted on the spraying end of a hose. These are usually aspiration devices in which a suction tube is used to draw the chemical out of a hose-mounted container and add it to the water stream (e.g., U.S. Pat. Nos. 3,042,314 and 2,991,939). Because of the suction action of these devices, the attitude of the aspiration dispenser is critical to its proper operation. Any tilting of the device might cause the liquid chemical to flow away from and expose the intake end of the suction tube. Suction would be lost, and the chemical flow would diminish or cease altogether. A further drawback of these dispensers is that the spray pattern of the hose nozzle cannot be adjusted during operation. The aspiration devices cannot tolerate the temporary back pressure caused by such an adjustment, and water may enter the chemical container and dilute the chemical therein.
An improvement on the above described aspiration devices embodies the use of a flexible bladder for containing the liquid chemical mounted in a bottle in such a way that liquid pressure may be applied between the exterior of the bag and the interior of the bottle to force the chemical into a stream of water to be there entrained and sprayed from a nozzle (e.g., U.S. Pat. Nos. 2,153,240 and 3,220,435). So far as I am aware, in this type of prior art device the proportions of chemical to water are not readily adjustable nor necessarily constant with varying water pressures. A further disadvantage of such systems as that of U.S. Pat. No. 2,153,240 resides in the fact that when the sprayer is turned off the system remains undesirably pressurized to the line pressure of the water supply.
Still another alternate type of dispenser is the compression sprayer. This device includes a large tank which holds the premixed chemicals and water. The tank, however, is expensive and because of its size is difficult to transport and store. As a result, the compression sprayer is not an acceptable alterative to the hose-mounted dispenser, particularly for those applications which would require infrequent and limited spraying.